Throughout our high school days, whenever there is a theory in which we use mass, we always studied rest mass. But how there is two kind of masses. To understand this firstly we have to understand what is mass according to classical physics.

Mass is both a property of a physical body and a measure of its resistance to acceleration (a change in its state of motion) when a net force is applied.
Okay till here everything is fine!!!
This definition of mass will be applicable to our normal world. But when we are discussing the topics like relativity and dealing with a velocity which is comparable with velocity of light, this ‘rest mass’ concept fails there.
Rest mass is the Newtonian mass as measured by an observer moving along with the object. Rest mass is the portion of the total mass of an object or system of objects that is independent of the overall motion of the system. More precisely, it is a characteristic of the system's total energy and momentum that is the same in all frames of reference related by Lorentz transformations. If a center-of-momentum frame exists for the system, then the invariant mass of a system is equal to its total mass in that "rest frame".
But relativistic mass is the mass used in theory of relativity. Relativistic mass is the total quantity of energy in a body or system divided by c2. The word mass is given two meanings in special relativity: one (rest or invariant mass, and its equivalent rest energy) is an invariant quantity which is the same for all observers in all reference frames; the other (relativistic mass or the equivalent total energy of the body) is dependent on the velocity of the observer.
Thanks for Reading!!!
Check out my other blog posts!!!
Don't forget to share this post in your social media handles to enrich everyone's knowlwdge!!!

You can directly talk with me on Instagram
To meet more physics Enthusiasts please join our Facebook Page 
Also for latest updates of my posts join me on Twitter

See you Again!!!!!

                                                                 -Ratnadeep Das Choudhury
                                                 Founder and writer of The Dynamic Frequency